Arq/harq-related procedure for grant-free random access

ABSTRACT

A user equipment, UE, for a wireless communication network including one or more base stations, performs a transmission to a base station using a grant-free, GF, transmission scheme. The transmission being performed in accordance with a GF transmission configuration. The UE receives from the base station a certain signaling. The certain signaling indicates that the base station failed to identify the UE from the transmission. Responsive to the certain signaling from the base station, the UE retransmits the transmission in accordance with a GF retransmission configuration. The GF retransmission configuration is different from the GF transmission configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of copending U.S. patent applicationSer. No. 17/092,911, filed on Nov. 9, 2020, which is continuation ofcopending International Application No. PCT/EP2019/062042, filed May 10,2019, which is incorporated herein by reference in its entirety, andadditionally claims priority from European Application No. EP18171864.4, filed May 11, 2018, which is also incorporated herein byreference in their entirety.

The present application concerns the field of wireless communications,more specifically the field of grant-free random access transmissions.Embodiments provide an ARQ/HARQ related procedure for a grant-freerandom access of UEs enabling unidentified UEs to retransmit thetransmission using a retransmission configuration different for thefirst transmission configuration. Other embodiments provide for anapproach allowing a joint receiver, for example to a base station of thewireless communication network, to reliably detect the occurrence ofgrant-free transmissions by UEs served by the base station.

BACKGROUND OF THE INVENTION

FIG. 1 is a schematic representation of an example of a terrestrialwireless network 100 including a core network 102 and a radio accessnetwork 104. The radio access network 104 may include a plurality ofbase stations gNB₁ to gNB₅, each serving a specific area surrounding thebase station schematically represented by respective cells 106 ₁ to 106₅. The base stations are provided to serve users within a cell. The termbase station, BS, refers to as gNB in 5G networks, eNB inUMTS/LTE/LTE-A/LTE-A Pro, or just BS in other mobile communicationstandards. A user may be a stationary device or a mobile device.Further, the wireless communication system may be accessed by mobile orstationary IoT devices which connect to a base station or to a user. Themobile devices or the IoT devices may include physical devices, groundbased vehicles, such as robots or cars, aerial vehicles, such as mannedor unmanned aerial vehicles (UAVs), the latter also referred to asdrones, buildings and other items or devices having embedded thereinelectronics, software, sensors, actuators, or the like as well asnetwork connectivity that enable these devices to collect and exchangedata across an existing network infrastructure. FIG. 1 shows anexemplary view of only five cells, however, the wireless communicationsystem may include more such cells. FIG. 1 shows two users UE₁ and UE₂,also referred to as user equipment, UE, that are in cell 106 ₂ and thatare served by base station gNB₂. Another user UE₃ is shown in cell 106 ₄which is served by base station gNB₄. The arrows 108 ₁, 108 ₂ and 108 ₃schematically represent uplink/downlink connections for transmittingdata from a user UE₁, UE₂ and UE₃ to the base stations gNB₂, gNB₄ or fortransmitting data from the base stations gNB₂, gNB₄ to the users UE₁,UE₂, UE₃. Further, FIG. 1 shows two IoT devices 110 ₁ and 110 ₂ in cell106 ₄, which may be stationary or mobile devices. The IoT device 110 ₁accesses the wireless communication system via the base station gNB₄ toreceive and transmit data as schematically represented by arrow 112 ₁.The IoT device 110 ₂ accesses the wireless communication system via theuser UE₃ as is schematically represented by arrow 112 ₂. The respectivebase station gNB₁ to gNB₅ may be connected to the core network 102, e.g.via the S1 interface, via respective backhaul links 114 ₁ to 114 ₅,which are schematically represented in FIG. 1 by the arrows pointing to“core”. The core network 102 may be connected to one or more externalnetworks. Further, some or all of the respective base station gNB₁ togNB₅ may connected, e.g. via the S1 or X2 interface or XN interface inNR, with each other via respective backhaul links 116 ₁ to 116 ₅, whichare schematically represented in FIG. 1 by the arrows pointing to“gNBs”. The wireless network or communication system depicted in FIG. 1may by an heterogeneous network having two distinct overlaid networks, anetwork of macro cells with each macro cell including a macro basestation, like base station gNB₁ to gNB₅, and a network of small cellbase stations (not shown in FIG. 1 ), like femto or pico base stations.

For data transmission a physical resource grid may be used. The physicalresource grid may comprise a set of resource elements to which variousphysical channels and physical signals are mapped. For example, thephysical channels may include the physical downlink and uplink sharedchannels (PDSCH, PUSCH) carrying user specific data, also referred to asdownlink and uplink payload data, the physical broadcast channel (PBCH)carrying for example a master information block (MIB) and a systeminformation block (SIB), the physical downlink and uplink controlchannels (PDCCH, PUCCH) carrying for example the downlink controlinformation (DCI), etc. For the uplink, the physical channels mayfurther include the physical random access channel (PRACH or RACH) usedby UEs for accessing the network once a UE synchronized and obtained theMIB and SIB. The physical signals may comprise reference signals (RS),synchronization signals and the like. The resource grid may comprise aframe or radioframe having a certain duration, like milliseconds, in thetime domain and having a given bandwidth in the frequency domain. Theframe may have a certain number of subframes of a predefined length,e.g., 2 subframes with a length of 1 millisecond. Each subframe mayinclude two slots of 6 or 7 OFDM symbols depending on the cyclic prefix(CP) length. A frame may also consist of a smaller number of OFDMsymbols, e.g. when utilizing shortened transmission time intervals(sTTI) or a mini-slot/non-slot-based frame structure comprising just afew OFDM symbols.

The wireless communication system may be any single-tone or multicarriersystem using frequency-division multiplexing, like the orthogonalfrequency-division multiplexing (OFDM) system, the orthogonalfrequency-division multiple access (OFDMA) system, or any otherIFFT-based signal with or without CP, e.g. DFT-s-OFDM. Other waveforms,like non-orthogonal waveforms for multiple access, e.g. filter-bankmulticarrier (FBMC), generalized frequency division multiplexing (GFDM)or universal filtered multi carrier (UFMC), may be used. The wirelesscommunication system may operate, e.g., in accordance with theLTE-Advanced pro standard or the 5G or NR, New Radio, standard.

In the wireless communication network as shown in FIG. 1 the radioaccess network 104 may be a heterogeneous network including a network ofprimary cells, each including a primary base station, also referred toas a macro base station. Further, a plurality of secondary basestations, also referred to as small cell base stations, may be providedfor each of the macro cells. In addition to the above describedterrestrial wireless network also non-terrestrial wireless communicationnetworks exist including spaceborne transceivers, like satellites,and/or airborne transceivers, like unmanned aircraft systems. Thenon-terrestrial wireless communication network or system may operate ina similar way as the terrestrial system described above with referenceto FIG. 1 , for example in accordance with the LTE-advanced pro standardor the 5G or NR, new radio, standard.

In a wireless communication network or system as described above onenetwork function is the random access, which is carried out by userswhen first accessing the system. In wireless communication networks,like 5G networks, the number of UEs may increase substantially whencompared to the number of UEs operated in current networks or systems,for example due to a massive access of internet-of-things (IoT)applications. In such a scenario, the random access of such a highnumber of UEs may be an issue. More specifically, a massive randomaccess paradigm, for example when considering IoT applications, ischaracterized by a huge number of UEs accessing sporadically thewireless channel of the system to transmit data. A contention-free,orthogonal multiple access protocol, such as TDMA, (O)FDMA, etc., maynot meet the requirements for allowing such a sporadic access, becausethe resources are assigned to the users in a fixed and centralizedmanner. Such an approach, inevitably, results in a large signalingoverhead, a high realization complexity and a low overall systemefficiency. Contention-based mechanisms, e.g., ALOHA or slotted ALOHA,on the other hand, may suffer from a throughput degradation in thepresence of a large or number of users due to the delay associated withthe back off/retransmission mechanisms implemented in suchcontention-based mechanisms.

In existing wireless communication networks or systems, like a long termevolution (LTE) system, the uplink transmission may be scheduled by anaccess point, AP, for example by the base station, using a request-grantprocedure. A user sends a scheduling request, SR, to the AP during theregistration procedure. Following the sending of the scheduling request,the AP performs the scheduling to grant resources to the users in acentralized manner. The request-grant procedure, i.e., the initialassociation to the network, is performed in a contention-based manner.

The same mechanism may be used to reestablish a connection upon failure.The contention-based random access procedure includes four steps. In afirst step, a preamble is transmitted by the user to the base station,eNB. In the second step, if the eNB detects the preamble, a randomaccess response is transmitted, followed by two further signaling steps.If the eNB is not detecting the preamble, a timeout occurs at the UE,and the UE transmits a further random access sequence of the samepreamble format.

In the presence of a massive number of devices or UEs which sporadicallyaccess the system, the contention-based random access procedure mayresult in a sharp degradation in performance and large access delaysrendering, as a consequence, the communication impractical, at least forcertain UE types or certain services, like ultra-reliable low latencycommunication, URLLC, services. To allow thousands of devices to accessa wireless communication system, a grant-free random access scheme maybe implemented allowing users to transmit to the AP simultaneously usinggrant-free resources which may be freely used by the respective UEs forthe transmission, i.e., resources that are not allocated by the basestation to a certain UE. Such a grant-free transmission may include,besides the data to be transmitted, also a user identity.

FIG. 2 schematically represents a transmission from UEs, UE₁, UE₂ . . .UE_(n), towards a base station BS using a grant-free random access. Theradio link RL is schematically represented and the resources availablefor the communication are indicated, for example respectivefrequency/time resources. In FIG. 2 , respective resource pools R₁ to R₃are indicated of which, for example, the resources in resource block R₂may be used by one or more of the UEs for a grant-free random access foran uplink transmission towards the base station BS, while one or more ofthe other resource pools R₁, R₃ may be used for a conventionalcommunication using resources allocated to the UEs by the base stationBS. In case of a grant-free uplink communication from one, some or allof the UEs, the uplink transmission uses the resources in resource poolR₂, and the base station BS detects active users or a subset thereof.The transmission may include the UE ID so that the base station BS mayidentify the UEs performing the grant-free transmission. The basestation may send a control message to each UE that has been identifiedby the base station, for example an acknowledgement, ACK, message. Thebase station may use a unicast HARQ ACK feedback towards the UEs whichhave been identified. In other words, the control message stating theACK is sent to each identified UE uniquely. The BS, in accordance withother examples, may send a multicast HARQ ACK feedback to all active UEsor users that were successfully decoded or detected. The multicast HARQACK feedback includes the identities of those UEs which have beenidentified by the base station.

However, for a subset of the UEs the base station BS may not be able todecode their transmissions on the respective grant-free resources, andthe base station does not identify the respective UEs as active users.As a consequence, such UEs do not receive the acknowledgement messagefrom the base station. Such a situation may occur, for example, when thesystem is overloaded. Those UEs which did not receive theacknowledgement message from the base station BS confirming that the UEhas been identified, repeat their uplink transmission in the grant-freeresource pool R₂ at the next random access opportunity or occasion.However, it is likely that at this point the system is still overloadedso that the probability that a non-identification of the UEs happensagain is quite high.

It is noted that the information in the above section is only forenhancing the understanding of the background of the invention andtherefore it may contain information does not form conventionaltechnology that is already known to a person of ordinary skill in theart.

SUMMARY

An embodiment provides a user equipment, UE, for a wirelesscommunication network including one or more base stations, wherein theUE is configured to perform a transmission to a base station using agrant-free, GF, transmission scheme, the transmission being performed inaccordance with a GF transmission configuration, wherein the UE isconfigured to receive from the base station a certain signaling, thecertain signaling indicating that the base station failed to identifythe UE from the transmission, and wherein, responsive to the certainsignaling from the base station, the UE is configured to retransmit thetransmission in accordance with a GF retransmission configuration, theGF retransmission configuration being different from the GF transmissionconfiguration.

According to another embodiment, a wireless communication system mayhave: one or more inventive UEs and one or more base stations, BSs,wherein the BS is configured to serve one or more UEs of the wirelesscommunication network, wherein a certain number of the UEs, which areserved by the BS, are configured to perform a transmission to the BSstation using a grant-free, GF, transmission scheme, the transmissionbeing performed in accordance with a GF transmission configuration, theBS is configured receive from the certain UEs respective grant freetransmissions and to determine whether the certain UEs can be identifiedfrom the grant free transmission, and in case some or all of the certainUEs cannot be identified by the BS, the BS is configured to transmit acertain signaling, the certain signaling indicating that the BS failedto identify the certain UEs from the transmission, and causing thecertain UEs to retransmit the transmission in accordance with a GFretransmission configuration, the GF retransmission configuration beingdifferent from the GF transmission configuration.

According to another embodiment, a method may have the steps of:performing by a user equipment, UE, of a wireless communication network,which includes one or more base stations, a transmission to a basestation using a grant-free, GF, transmission scheme, the transmissionbeing performed in accordance with a GF transmission configuration,receiving, at the UE, from the base station a certain signaling, thecertain signaling indicating that the base station failed to identifythe UE from the transmission, and responsive to the certain signalingfrom the base station, retransmitting, by the UE, the transmission inaccordance with a GF retransmission configuration, the GF retransmissionconfiguration being different from the GF transmission configuration.

Another embodiment may have a non-transitory digital storage mediumhaving a computer program stored thereon to perform the inventive methodwhen said computer program is run by a computer.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequentlyreferring to the appended drawings, in which:

FIG. 1 shows a schematic representation of an example of a terrestrialwireless communication system;

FIG. 2 schematically represents a transmission from a plurality of UEstowards a base station BS using a grant-free random access;

FIG. 3 is a schematic representation of a wireless communication systemfor communicating information between a transmitter, which may operatein accordance with the inventive teachings described herein, and aplurality of receivers, which may operate in accordance with theinventive teachings described herein;

FIG. 4 is a flow diagram illustrating an ARQ/HARQ-related procedure fora grant-free random access in accordance with embodiments of the presentinvention;

FIG. 5 part 1 and part 2 collectively comprise FIG. 5 and illustrate anembodiment for increasing the pool size for the grant-freeretransmission;

FIGS. 6A and 6B illustrate embodiments of a GF re/transmission timing inaccordance with the inventive approach, wherein FIG. 6(a) illustrates anembodiment in which a GF retransmission occasion is earlier or laterthan a GF transmission occasion, FIG. 6(b) illustrates an embodiment inwhich a GF retransmission occasion is earlier than a GF transmissionoccasion;

FIG. 7 shows an example of a UE-specific RRC signaling for indicating aplurality of grant-free retransmission pool IDs in accordance withembodiments of the present invention; and

FIG. 8 illustrates an example of a computer system on which units ormodules as well as the steps of the methods described in accordance withthe inventive approach may execute.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention are now described in more detailwith reference to the accompanying drawings in which the same or similarelements have the same reference signs assigned.

First Aspect

In a cellular wireless network, like a network described above withreference to FIG. 1 and to FIG. 2 , when implementing a grant-freetransmission scheme for an uplink transmission from one or more users toa receiver, it may occur, e.g., when the cell served by a base stationis overloaded, that only some of the UEs performing the grant-freeuplink transmission towards the receiver are actually identified, andthe remaining UEs operating on the basis of the grant-free transmissionscheme, which are not identified, repeat the grant-free uplinktransmission at the next opportunity. However, in case the specificsituation which resulted in the detection/identification of only asubset of the UEs performing the grant-free, GF, uplink transmissiondoes not change, it is likely that the same will happen again, i.e.,again only a subset of the GF-UEs (UEs performing an uplink transmissionusing grant-free resources) will be identified. Thus, UEs may experiencedelays in the uplink transmission which may not be acceptable forcertain types of UEs or certain services implemented in the UEs, forexample URLLC services.

The present invention is based on the finding that the above describedproblem is due to the fact that a GF-UE, which is not identified at theBS, uses the same parameters for the initial or first transmission andfor the retransmission at the next opportunity for the grant-freeaccess. To address this problem, in accordance with a first aspect ofthe present invention, the base station determines that for certainuplink transmissions on the resources allocated for the grant-freeaccess, for example resources in resource block R₂ (see FIG. 2 ), theusers performing the uplink transmission cannot be identified.Responsive to this determination the base station is aware that thereare some UEs that try to access the base station using the grant-freeaccess scheme, and sends a certain signaling, e.g., a broadcast message,indicating to the UEs in the coverage of the base station anidentification of at least some of the UEs using the GF-resourcesfailed. For example, a group non-acknowledgement, NACK, message may besent via a broadcast signaling to all UEs. Responsive to such a groupNACK message (certain signaling), those UEs which recognize that theiruplink transmission has not been identified at the base station maychange the current transmission configuration for the grant-free uplinktransmission, also referred to as the GF transmission configuration, toa new or modified transmission configuration for the retransmission,also referred to as the GF retransmission configuration. The GFretransmission configuration is applied when retransmitting thetransmission at the next opportunity for a grant-free access to the basestation.

In accordance with the inventive approach, causing a modification of thegrant-free transmission parameters so as to obtain grant-freeretransmission parameters which are different from the initialparameters or the parameters used during the last grant-freetransmission, the probability that the UE will be not identified againmay be lowered, thereby improving the system performance, especially forlatency sensitive transmissions by certain types of UEs or by certainservices implemented by the UEs.

Embodiments of the present invention may be implemented in a wirelesscommunication system or network as depicted in FIG. 1 or FIG. 2including transmitters or transceivers, like base stations, andreceivers or users, like mobile or stationary terminals or IoT devices,as mentioned above. FIG. 3 is a schematic representation of a wirelesscommunication system for communicating information between a transmitter200, like a base station, and a plurality of receivers 202 ₁ to 202_(n), like UEs, which are served by the base station 200. The basestation 200 and the UEs 202 may communicate via a wireless communicationlink or channel 204, like a radio link. The base station 200 includesone or more antennas ANT_(T) or an antenna array having a plurality ofantenna elements, and a signal processor 200 a. The UEs 202 include oneor more antennas ANT_(R) or an antenna array having a plurality ofantennas, and a signal processor 202 a ₁, 202 a _(n). The base station200 and the respective UEs 202 may operate in accordance with theinventive teachings described herein.

User Equipment

In accordance the first aspect, the present invention provides a userequipment, UE, for a wireless communication network including one ormore base stations 200. The UE 202 performs a transmission to a basestation 200 using a grant-free, GF, transmission scheme. Thetransmission is performed in accordance with a GF transmissionconfiguration. The UE 202 is configured to receive from the base station200 a certain signaling. The certain signaling indicates that the basestation failed to identify the UE 202 from the transmission. Responsiveto the certain signaling from the base station 200, the UE 202retransmits the transmission in accordance with a GF retransmissionconfiguration. The GF retransmission configuration is different from theGF transmission configuration.

In accordance with embodiments, the GF transmission configurationincludes a GF transmission resource or a GF transmission resource pool,and the GF retransmission configuration includes a GF retransmissionresource or a GF retransmission resource pool.

In accordance with embodiments, the GF retransmission resource pool islarger than the GF transmission resource pool.

In accordance with embodiments, the GF retransmission resource poolincludes the GF transmission resource pool and additional resources, orthe GF retransmission resource pool includes resources different fromthe GF transmission resource pool.

In accordance with embodiments, the UE is configured to select the GFretransmission resource randomly from the GF retransmission resourcepool.

In accordance with embodiments, the GF retransmission resource poolincludes a plurality of retransmission resource pools, the plurality ofretransmission resource pools being of the same size or of differentsizes, and the plurality of retransmission resource pools including afirst GF retransmission resource pool and second GF retransmissionresource pool.

In accordance with embodiments, the UE is configured to select the GFretransmission resource from first GF retransmission resource pool andfrom second GF retransmission resource pool

-   -   randomly, or    -   based on a UE-ID or group/service type, e.g. UEs of a certain        type use the first GF retransmission resource pool, and other        UEs use the second GF retransmission resource pool.

In accordance with embodiments, the GF retransmission resource poolincludes at least one further GF retransmission resource pool.

In accordance with embodiments, the GF transmission configurationincludes a GF transmission coding scheme, and the GF retransmissionconfiguration includes a GF retransmission coding scheme, the GFtransmission coding scheme being different from the GF retransmissioncoding scheme.

In accordance with embodiments, the GF transmission coding schemeincludes a first NOMA sequence, and the GF retransmission coding schemeincludes a second NOMA sequence, the second NOMA sequence being morerobust than the first NOMA sequence, e.g., by using a lower code rate.

In accordance with embodiments, the GF transmission configurationincludes a time at which the transmission is performed, and the GFretransmission configuration includes a plurality of time offsets forthe retransmission relative to the time of the transmission.

In accordance with embodiments, the UE is configured to select, based ona UE-ID or a group/service type, from the plurality of time offsets

-   -   randomly a time offset for the retransmission, or    -   a preconfigured time offset for the retransmission.

In accordance with embodiments, UEs of a certain type use apreconfigured time offset, and other UEs use a random time offset.

In accordance with embodiments, the GF transmission configurationincludes or identifies a plurality of grant-free access occasions duringwhich grant-free transmissions are to be performed, the plurality ofgrant-free access occasions including at least a first grant-free accessoccasion and a second grant-free access occasion, and the GFretransmission configuration includes or identifies at least one furthergrant-free access occasion during which grant-free retransmissions areto be performed, the further grant-free access occasion being differentfrom the second grant-free access occasion.

In accordance with embodiments, first UEs, e.g., latency sensitive UEsor services, like URLLC services, use a further grant-free accessoccasion that is earlier than the second grant-free access occasion, andsecond UEs, e.g., less sensitive UEs or services, like enhanced MobileBroadBand, eMBB, massive Machine-Type Communication, mMTC, or IoTs, usea further grant-free access occasion that is later or earlier than thesecond grant-free access occasion.

In accordance with embodiments, the UE is preconfigured with a pluralityof GF retransmission configurations, e.g., using an UE specific RRCsignaling, and the UE is configured to receive a control message, like aDCI message, indicating which of the plurality of GF retransmissionconfigurations is to be used by the UE responsive to the certainsignaling.

In accordance with embodiments, a pre-configuration message indicates aplurality of GF retransmission pools, and the control message indicatesone or more GF retransmission pools, and wherein the UE is configured touse, responsive to the certain signaling,

-   -   the GF retransmission pool indicated in the control message, or    -   in case no GF retransmission pool is indicated in the control        message, a preconfigured default GF retransmission pool or the        UE may randomly select one of the retransmission pools defined        by the RRC signaling.

In accordance with embodiments, the UE is configured to receive acontrol message, like a DCI message, indicating a plurality of GFretransmission configurations, and wherein the certain signalingindicates which of the plurality GF retransmission configurations is tobe used by UE responsive to receiving the certain signaling.

In accordance with embodiments, the DCI indicates a plurality of GFretransmission pools.

In accordance with embodiments, control message indicates the GFtransmission pool explicitly or implicitly, e.g., using RNTI.

In accordance with embodiments, the certain signaling includes the GFretransmission configuration to be used by UE responsive to receivingthe certain signaling

In accordance with embodiments, the certain signaling indicates the GFresource associated with the transmission, and responsive to the certainsignaling, the UE is configured to determine that the base station didnot receive anything and is not aware of the transmission of the UE.

In accordance with embodiments, the transmission includes an UEidentifier, e.g., a UE-specific DeModulation Reference Signal, DMRS.

In accordance with embodiments, the certain signaling comprises abroadcast NACK message transmitted by the base station to a plurality ofUEs in wireless communication network.

In accordance with embodiments, the user equipment comprises one or moreof:

-   -   a mobile or stationary terminal,    -   cellular IoT-UE    -   an IoT device,    -   a ground based vehicle,    -   an aerial vehicle,    -   a drone,    -   a building, or    -   any other item or device provided with network connectivity        enabling the item/device to communicate using the wireless        communication network, e.g., a sensor or actuator.

Base Station

In accordance the first aspect, the present invention provides a basestation, BS, for a wireless communication system including one or morebase stations. The base station 200 serves one or more UEs 202 of thewireless communication network. A certain number of the UEs 202, whichare served by the base station 200, perform a transmission to the basestation 200 using a grant-free, GF, transmission scheme. Thetransmission is performed in accordance with a GF transmissionconfiguration. The base station 200 receives from the certain UEs 202respective grant-free transmissions and determines whether the certainUEs can be identified from the grant-free transmission. In case some orall of the certain UEs cannot be identified by the base station 200, thebase station 200 transmits a certain signaling. The certain signalingindicates that the base station 200 failed to identify the certain UEsfrom the transmission. This certain signaling causes the certain UEs toretransmit the transmission in accordance with a GF retransmissionconfiguration. The GF retransmission configuration may be different fromthe GF transmission configuration.

In accordance with embodiments, the transmissions from the certain UEsinclude respective UE identifiers.

In accordance with embodiments, the certain signaling comprises abroadcast NACK message transmitted by the base station to the certainUEs in wireless communication network.

In accordance with embodiments, the certain UEs comprise one, some orall of the UEs served by the BS.

In accordance with embodiments, the certain signaling indicates the GFresource associated with the transmissions.

In accordance with embodiments, the certain signaling includes the GFretransmission configuration to be used by UE responsive to receivingthe certain signaling.

In accordance with embodiments, the GF transmission configurationincludes a GF transmission resource or a GF transmission resource pool,and the GF retransmission configuration includes a GF retransmissionresource or a GF retransmission resource pool.

In accordance with embodiments, the GF retransmission resource pool islarger than the GF transmission resource pool.

In accordance with embodiments, the GF retransmission resource poolincludes the GF transmission resource pool and additional resources, orthe GF retransmission resource pool includes resources different fromthe GF transmission resource pool.

In accordance with embodiments, the GF retransmission resource poolincludes a plurality of retransmission resource pools, the plurality ofretransmission resource pools being of the same size or of differentsizes, and the plurality of retransmission resource pools including afirst GF retransmission resource pool and second GF retransmissionresource pool.

In accordance with embodiments, the GF retransmission resource poolincludes at least one further GF retransmission resource pool

In accordance with embodiments, the GF transmission configurationincludes a GF transmission coding scheme, and the GF retransmissionconfiguration includes a GF retransmission coding scheme, the GFtransmission coding scheme being different from the GF retransmissioncoding scheme.

In accordance with embodiments, the GF transmission coding schemeincludes a first NOMA sequence, and the GF retransmission coding schemeincludes a second NOMA sequence, the second NOMA sequence being morerobust than the first NOMA sequence, e.g., by using a lower code rate.

In accordance with embodiments, the GF transmission configurationincludes a time at which the transmission is performed, and the GFretransmission configuration includes a plurality of time offsets forthe retransmission relative to the time of the transmission.

In accordance with embodiments, the GF transmission configurationincludes or identifies a plurality of grant-free access occasions duringwhich grant-free transmissions are to be performed, the plurality ofgrant-free access occasions including at least a first grant-free accessoccasion and a second grant-free access occasion, and the GFretransmission configuration includes or identifies at least one furthergrant-free access occasion during which grant-free retransmissions areto be performed, the further grant-free access occasion being differentfrom the second grant-free access occasion.

In accordance with embodiments, the base station comprises one or moreof:

-   -   a macro cell base station, or    -   a small cell base station, or    -   a UE, or    -   an AMF, or    -   an SMF, or    -   a core network entity, or    -   any transmission/reception point (TRP) enabling an item or a        device to communicate using the wireless communication network,        the item or device being provided with network connectivity to        communicate using the wireless communication network.

Computer Program Product

The present invention provides a computer program product comprisinginstructions which, when the program is executed by a computer, causesthe computer to carry out one or more methods in accordance with thepresent invention.

Embodiments of the first aspect inventive approach are now be describedin more detail, and FIG. 4 is a flow diagram illustrating theARQ/HARQ-related procedure for a grant-free random access in accordancewith embodiments of the present invention. At block 220 a grant-freetransmission is performed by one or more active users of a wirelesscommunication system, for example a wireless communication system asdescribed above with reference to FIG. 1 , FIG. 2 or FIG. 3 . Thegrant-free transmission may be performed at specific times or forspecific time periods, or, more generally, at predefined grant-freetransmission occasions. The UEs of the wireless communication systemwhich perform an uplink transmission using a grant-free transmissionscheme are also referred to as GF-UEs. At block 220 one more of theGF-UEs perform a grant-free transmission towards the base station which,at block 222 determines whether the transmissions recognized on thegrant-free resources allocated for the grant-free transmission can beidentified, i.e., can be associated with the respective GF-UEs. In casea GF-UE is identified, the base station sends an acknowledgementmessage, for example, a HARQ-ACK message to the identified GF-UE as isindicated at 224. In accordance with further embodiments, rather thansending a unicast HARQ ACK feedback at block 224 also a multicast HARQACK feedback may be transmitted. The receiver or base station may send amulticast ACK to the active users that were successively decoded statingthe corresponding IDs, UE identities, of the successively decoded activeusers.

In case one or more of the GF-UEs are not identified at the basestation, i.e., in case transmissions are recognized at the base stationon the respective grant-free resources, which cannot be associated witha certain user, the base station 200 determines that not all of the UEsusing the grant-free uplink transmission were successfully detected ordecoded. In this situation, in accordance with embodiments of thepresent invention, a multicast HARQ NACK feedback is generated at block226, which is also referred to as a group NACK or a certain signaling.The group NACK is broadcast so as to be received by all UEs served bythe base station, and those UEs that did not receive a HARQ ACK feedback(block 224) and that performed an uplink transmission determine that thebase station did not identify/receive their transmission. The group NACKwhich may be broadcast at block 226 causes a retransmission of theuplink transmission as is indicated at block 228 using differentparameters. For example, a first or initial grant-free uplinktransmission by a UE is performed on the basis of a transmissionconfiguration, also referred to as a GF transmission configuration.Responsive to the group NACK a UE, which realizes that it has not beenidentified at the base station, causes the retransmission at block 228but uses a different configuration, also referred to as a GFretransmission configuration.

To allow for the identification of the UEs at the base station duringthe grant-free uplink transmission, in accordance with embodiments, theuplink transmission may include the UE ID, the UE identifier, which thebase station, upon a successful detection and decoding of thetransmission may evaluate so as to provide to the identified UE, on thebasis of the identifier, the acknowledgement message (block 224). Incase the base station realizes that there is some kind of transmissionbut cannot decode the UE identifier, the group NACK message at block 226is generated.

In accordance with embodiments of the present invention, the group NACKmay include the GF retransmission configuration, i.e., the base stationsignals towards the respective UEs the parameters or configuration forperforming the retransmission which is different from the precedingtransmission configuration.

In accordance with other embodiments, the respective UEs may bepreconfigured with one or more possible GF retransmission configurationsand, responsive to the receipt of the group NACK, one of thepreconfigured GF retransmission configuration for performing theretransmission at block 228 may be selected at the UE.

The use of a GF retransmission configuration that is different from theGF transmission configuration allows for an improvement of the systemperformance as the likelihood that the UEs are still not identified atthe next possibility or occasion for a grant-free access is reduced asdifferent parameters or configurations are used. Thus, despite the factthat the overall situation of the network, for example, the loadsituation, may not have changed, due to the change in the configurationused for the grant-free uplink transmission more UEs may be identifiedat the base station.

In accordance with embodiments, the base station may send the broadcastNACK message together with an indication of the grant-free resource, GFresource, so that the UEs that transmitted on this GF resource and thatdid not receive a ACK feedback know that the BS is not aware of thetransmission of the UE, and that a retransmission is needed.

GF Re/Transmission Resources/Resource Pools

In accordance with embodiments, the GF retransmission configuration mayinclude one or more GF retransmission resources to be used by the UEsthat used the first resource indicated by the GF transmissionconfiguration. The broadcast control message may include informationabout the new GF retransmission resource or the receipt of the broadcastcontrol message, the NACK message, may cause the UE to select a GFretransmission resource with which the UE is preconfigured.

In accordance with further embodiments, rather than using a GFtransmission resource or a GF retransmission resource, a GF transmissionresource pool and a GF retransmission resource pool may be provided, andfor the first GF transmission a UE may use one or more resourcesselected from the GF transmission resource pool, and for theretransmission, the UE may use one or more resources from the GFretransmission resource pool.

Responsive to the signaling from the base station, for exampleresponsive to receiving the broadcast NACK message, the pool parametersmay be modified, for example by increasing the GF transmission pool sizeto obtain the GF retransmission pool. For example additional frequencyand/or time resources may be provided. FIG. 5 illustrates an embodimentfor increasing the pool size for the retransmission. In the left part ofFIG. 5 , the initial or first resource pool is indicated together withrespective NOMA-sequence IDs. Responsive the group NACK message thefirst resource pool is increased, and in accordance with the embodimentdepicted in FIG. 5 the size of the first resource pool is doubled, so asto increase the robustness of the retransmission by a higher spreadingfactor.

In accordance with embodiments, together with the increase in pool sizealso a preconfigured, more robust NOMA sequence may be used for theretransmission. For example, the UE may use a first NOMA sequence forperforming the first transmission, and the UE may be preconfigured withthe second NOMA sequence for the retransmission, which is only used incase a broadcast NACK control message is received. In accordance withother embodiments, rather than NOMA sequences also other coding schemesmay be used. The more robust NOMA scheme is achieved by a lower codingrate of the second NOMA sequence, as may be seen from a comparison ofthe respective NOMA sequence IDs of FIG. 5 for the first transmissioncase and for the retransmission case.

In accordance with other embodiments, the GF retransmission resourcepool may include a plurality of GF retransmission resource pools, forexample at least a first pool and a second pool. For example, the firstpool may be the resource pool indicated in the left part of FIG. 5 andthe second pool for the retransmission may be increased in size as shownin the right part of FIG. 5 . Thus, the two pools may have differentNOMA parameters. However, in accordance with other embodiments, the atleast two GF retransmission resource pools may be of the same size andhave the same NOMA parameters. For example, the retransmission resourcepool shown in the right part of FIG. 5 may be split into two partshaving the same size or having different sizes.

In accordance with yet further embodiments, more than two pools may beprovided, for example, an additional third GF retransmission resourcepool may be provided.

In accordance with embodiments, the UE may randomly select one of theplurality of GF retransmission resource pools to use one or moreresources for performing the retransmission.

In accordance with other embodiments, a single retransmission resourcepool may be partitioned, and the partitions may be associated withrespective UEs dependent on a UE-ID, like a UE specific DMRS, ordependent on a group or service type to which the UE belongs. Inaccordance with other embodiments, respective pools of the plurality ofGF retransmission resource pools may be associated with respective UEsdependent on a UE-ID, like a UE specific DMRS, or dependent on a groupor service type to which the UE belongs. For example, a first, largerpartition or a first, larger pool of retransmission resources may beused for specific UEs or services, like URLLC, and the remainingpartitions or pools may be used for other kinds of UEs.

In accordance with other embodiments, specific UEs, for examples UEs ofa specific type or performing a specific service, may use the increasedre-transmission pool as indicated in FIG. 5 , while the remaining UEswhich may not be so critical regarding the latency or the like, may useagain the resources from the first transmission pool at the nextoccurrence of a grant-free uplink transmission. In other words, inaccordance with embodiments, not all of the UEs which have not beenidentified following the first transmission at the base station use theretransmission resource pool, rather, only those UEs for which areliable uplink transmission is decisive may use the retransmission poolwhile the remaining UEs may continue to use the original pool. Thus, forsome of the UEs, the transmission resources may change while they may donot change or remain fixed for the other UEs.

GF Re/Transmission Back Off Procedure

In accordance with yet other embodiments, the GF retransmissionconfiguration may define a back off procedure using a random orpreconfigured back off timer so that, for example, dependent on the UEID or the service type, a time offset between a time, at which the firsttransmission during the grant-free transmission period occurred, and atime is determined, at which the retransmission during the nextpossibility of the grant-free uplink transmission occurs. For example,UEs of a certain type for performing a certain services, for exampleURLLC UEs, may have associated an offset different from the other UEs soas to more reliably perform the grant-free uplink transmission.

GF Re/Transmission Timing

In accordance with yet further embodiments, the GF transmissionconfiguration may identify a plurality of grant-free access occasionsduring which grant-free transmissions are to be performed. The pluralityof grant-free access occasions includes at least a first grant-freeaccess occasion and a second grant-free access occasion. The GFretransmission configuration may identify at least one furthergrant-free access occasion during which grant-free retransmissions areto be performed. The further grant-free access occasion is differentfrom the second grant-free access occasions. In other words, the GFtransmission configuration defines the next GF occasion, i.e., the GFoccasion following the current GF occasion. The GF occasion defined bythe GF transmission configuration may identify which GF occasions are tobe used and which GF occasions are skipped. Responsive to the certainsignaling from the base station, the GF occasion as defined by the GFtransmission configuration may be modified using the GF retransmissionconfiguration that identifies a different GF occasion to be used for aretransmission.

In accordance with embodiments, a GF occasion may comprise one or moreresources in a time/frequency grid.

FIG. 6 illustrates embodiments of the GF re/transmission timing inaccordance with the inventive approach. For example, latency sensitiveUEs or services, like URLLC services, may use for the retransmission agrant-free access occasion as defined by the GF retransmissionconfiguration that is earlier than the second grant-free access occasiondefined by GF transmission configuration, while less sensitive UEs orservices, like enhanced Mobile BroadBand, eMBB, massive Machine-TypeCommunication, mMTC, or IoTs, may use a further grant-free accessoccasion as defined by the GF retransmission configuration that is lateror earlier than the second grant-free access occasion.

FIG. 6(a) illustrates a first grant-free access occasion 250 and asecond grant-free access occasion 252 as defined by the GF transmissionconfiguration during which grant-free transmissions may be performed bythe UE. Responsive to the certain signaling, in accordance withembodiments, the UE may modify the second grant-free access occasion 252in accordance with the GF retransmission configuration to a firstfurther grant-free access occasion 254 that is earlier than the occasion252, or to a second further grant-free access occasion 256 that is laterthan the occasion 252. This may be done dependent of the type of UE orservice, as mentioned above.

FIG. 6(b) illustrates another embodiment in which, similar to FIG. 6(a),the GF transmission configuration defines the first grant-free accessoccasion 250 and the second grant-free access occasion 252 during whichgrant-free transmissions may be performed by the UE. Responsive to thecertain signaling, in accordance with embodiments, the UE may modify thesecond grant-free access occasion 252 in accordance with the GFretransmission configuration to a further, earlier grant-free accessoccasions 258 or to a further, later grant-free access occasions 260,both of which are earlier than the occasion 252. Again, this may be donedependent of the type of UE or service, as mentioned above. Inaccordance with other embodiments, the further earlier and latergrant-free access occasions 258, 260, as defined by the GFretransmission configuration, may both be later than the occasion 252.

RRC Configured GF Retransmission Configuration

In accordance with embodiments, the GF retransmission configuration maybe RRC configured. A UE-specific RRC signaling may preconfigure the UEwith possible retransmission configurations, and responsive to a DCImessage a specific one of the plurality of GF retransmissionconfigurations is selected to be used in response to the receipt of thebroadcast NACK message from the base station. For example, whenconsidering a GF retransmission resource pool, also referred to as abackup retransmission pool, the UE-specific RRC signaling may indicate aplurality of pool IDs defining the resource pool to be used for theretransmission, for example an increase of an initial pool or theprovision of a plurality of pools or the partition of a pool or thelike. FIG. 7 shows an example of a UE-specific RRC signaling forindicating a plurality of pool IDs in accordance with embodiments of thepresent invention.

When using a UE-specific RRC signaling as the one depicted in FIG. 7 , aDCI message may be used for selecting the pool of resources to beactually used in response to the NACK message. For example, a DCI formatin the PDCCH common search space scrambled with a preconfigured RNTIthat is common for all GF-UEs may indicate the initial or first GFtransmission pool, and a pool ID for the retransmission pool to be used,for example Pool ID 1, Pool ID 2, . . . Pool ID N.

In accordance with embodiments, the original GF pool may be implicitlysignaled via the RNTI. In case the DCI message does not include anyentry for the pool ID a default retransmission pool may be used, or theUE may randomly select one of the retransmission pools defined by theRRC signaling.

DCI Configured GF Retransmission Configuration

In accordance with other embodiments, the retransmission pool may be DCIconfigured. In such embodiments, the DCI message may be sent as a DCIformat in the PDCCH common search space and is scrambled with apreconfigured RNTI that is common for all GF-UEs that are supposed toreceive the DCI, for example all UEs that are allowed to perform agrant-free uplink transmission to the base station. The DCI messageincludes the initial or first GF transmission pool and theretransmission pool parameters for the different pools available fromwhich one is selected responsive to the NACK message. In accordance withother embodiments, the original GF retransmission pool may be signaledimplicitly via the RNTI.

With regard to the above described embodiments concerning an RRCconfigured or DCI configured retransmission pool, it is noted that alsothe other GF retransmission configurations described above may beconfigured in either of the above described ways.

In accordance with embodiments, the change of the GF transmissionconfiguration or strategy to the GF retransmission configuration orstrategy may be signaled via a global codebook known to the base stationand the served UEs, or it may be generated on the fly per UE or group.In the latter case, past transmission/retransmission configurations maybe indexed, and it may be signaled that a certaintransmission/retransmission configuration or strategy from a predefinednumber of TTIs back in time is to be used. In such an embodiment, thebase station and the UEs keep track on the respectivetransmission/retransmission configurations or strategies used duringpreceding TTIs.

Second Aspect

In accordance with the second aspect, the present invention addresses aproblem that a base station may not distinguish between totally empty GFresources and overloaded GF resources. In both scenarios, the basestation does not decode any data or information because in the firstscenario there is no data to be decoded, and in the second scenario thedata cannot be decoded due to the overloaded GF resource pool. This maymake it difficult to properly evaluate, for example, the utilization ofa resource pool, to properly detect an inter-cell interference, and/orto properly detect traffic types.

User Equipment

To address this problem, in accordance the second aspect, the presentinvention provides a user equipment, UE, as it is shown in FIG. 3 , fora wireless communication network including one or more base stations andUEs, wherein a plurality of UEs is served by a base station and isconfigured to perform a grant-free transmission to the serving basestation. The UE 202 performs a grant-free data transmission to the basestation 200 using a grant-free, GF, transmission scheme. The UE 202transmits, responsive to a grant-free data transmission, a predefinedsignal to the base station 200 using a predefined grant-free resource.All UEs 202, which are served by the BS 200 and which perform agrant-free data transmission, transmit the same predefined signal on thesame predefined grant-free resource. The predefined signal allows thebase station 200 to determine that a grant-free transmission occurs.

In accordance with embodiments, the grant-free resource is a resourceselected from a grant-free resource pool.

In accordance with embodiments, the UE is configured to select apredefined signal from a plurality of predefined signals dependent onthe UE type or dependent on a service provided by the UE, therebyallowing the base station to discriminate UEs of different types.

Base Station

In accordance the second aspect, the present invention provides a basestation, BS, as it is shown in FIG. 3 , for a wireless communicationnetwork including one or more base stations and a plurality of UEs. TheBS 200 serves one or more UEs 202 of the wireless communication network.A certain number of the UEs 202, which are served by the BS 200, performa grant-free transmission to the base station 200 and transmit,responsive to a grant-free data transmission, a predefined signal to thebase station 200 using a predefined grant-free resource so that all ofthe certain UEs 200 transmit the same signal on the same predefinedgrant-free resource. The BS 200 receives from the certain UEs 202 therespective predefined signals on the predefined grant-free resource soas to detect that a grant-free transmission from the certain UEs 202occurs.

In accordance with embodiments, in case the base station detects that agrant-free transmission from the certain UEs occurs and no grant-freetransmission from the certain UEs can be successfully decoded, the basestation is configured to determine overloading.

In accordance with embodiments, responsive to determining theoverloading, the BS is configured to allocate more resources, e.g.,time-frequency resources, or increase a resource pool for the GF access,and/or assign to one or more of the certain UEs dedicated resourcesoutside the GF resources.

In accordance with embodiments, all of the certain UEs transmit togetherwith the same signal a UE-ID, and wherein, in case the base stationdetects that a grant-free transmission from the certain UEs occurs and agrant-free transmission can be successfully decoded from a subset of thecertain UEs, the base station is configured to determine a degree ofoverloading.

In accordance with embodiments, the BS is configured to decrease anoverloading factor to improve the reception quality, if overloading isdetected, and to increase the overloading factor for having a moreefficient transmission, if underloading is detected.

In accordance with embodiments, certain UEs from a neighboring cell usea further predefined signal different for the predefined signal used bythe certain UEs served by the base station, and wherein, based on thereceived predefined signals and further predefined signals, the BS isconfigured to detect an inter-cell interference.

In accordance with embodiments, using the detected inter-cellinterference, the BS is configured to use a sequence for identifying UEsserved by the base station which is different from a sequence used by aneighboring cell for identifying certain UEs from the neighboring cell.

In accordance with embodiments, the certain UEs transmit a predefinedsignal selected from a plurality of predefined signals dependent on theUE type or dependent on a service provided by the UE, and wherein, usingthe different predefined signals, the BS is configured to detect traffictypes.

In accordance with embodiments, using the detected traffic types, the BSis configured to use first sequences for identifying UEs of a firsttype, e.g., URLLC devices, and second sequences for identifying UEs of asecond type, e.g., eMBB devices, and/or allow special procedures for UEsof a certain type, e.g., UEs handling latency critical traffic, like anevacuation of retransmission resources (pre-emption).

Thus, in accordance with the second aspect of the present invention, thesignaling received from the GF-UEs allows the base station to determinethat a GF transmission occurs. In accordance with embodiments, the aimis not to identify the UEs, but to detect if there is any grant-freetransmission at all which is achieved by causing the UEs to transmit allthe same signal on the same predefined resource.

Evaluation of Pool Utilization

In accordance with embodiments of the second aspect of the inventiveapproach an evaluation of a GF-pool utilization may be performed as nowthe base station can distinguish between totally empty GF resources andoverloaded GF resources, and an overloading of the GF resources can bedetected.

In accordance with embodiments, the certain UEs transmit together withthe same signal a UE-ID, so that the base station may identify at leastsome of the UEs detects which allows determining a degree ofoverloading.

In accordance with further embodiments, the base station, responsive tothe detected overloading or to the determined degree of overloading, mayperform a mitigation to allocate more time-frequency resources for theGF access to cope with the overloading issue. In accordance withembodiments, some of the identified UEs may be assigned dedicatedresources so that they do not occupy the GF resources.

In accordance with other embodiments, the base station, responsive tothe detected overloading or to the determined degree of overloading, maylower an overloading factor to improve the reception quality. Ifunderloading is detected, the overloading factor may be increased forhaving a more efficient transmission.

Further, this allows the base station to calculate the Channel BusyRatio (CBR).

Detection of Inter-Cell Interference, ICI

In accordance with embodiments of the second aspect of the inventiveapproach an ICI may be detected performed as now the base station candistinguish between the UEs it serves and which use a first predefinedsignal and UEs served by a neighboring cell or base station which use asecond predefined signal.

In accordance with embodiments, the interference may be measured so thatthe network may coordinate the power control over the cells. This isadvantageous as it avoids that each cell is increasing its transmitpower independently because of a bad reception which would lead to aheavy cell interference.

Responsive to the ICI the BS may employ a sequence for identifying UEsserved by the base station which is different from a sequence used by aneighboring cell for identifying certain UEs from the neighboring cell.For example, a sequence may be used that is distinguishable for the BSfrom other sequences, e.g., Zadoff-Chu sequences with different cyclicshifts. In accordance with other examples, a completely differentsequence may be used for the identification. This minimizes interferenceof neighboring cells because when using for all UEs of neighboring cellsthe same sequence on the same resource, the measurements of each of thecells would be polluted by cell-edge UEs belonging to another cell.

Improved Detection of Traffic Types

In accordance with embodiments of the second aspect of the inventiveapproach certain UEs may transmit a predefined signal selected from aplurality of predefined signals dependent on the UE type or dependent ona service provided by the UE, so that the BS may detect traffic types.

For example, dependent on the detected traffic types, the BS may usefirst sequences for identifying UEs of a first type, e.g., URLLCdevices, and second sequences for identifying UEs of a second type,e.g., eMBB devices. According to other examples, the BS may allow forspecial procedures for UEs of a certain type, e.g., UEs handling latencycritical traffic, like an evacuation of retransmission resources(pre-emption).

Although some aspects of the described concept have been described inthe context of an apparatus, it is clear that these aspects alsorepresent a description of the corresponding method, where a block or adevice corresponds to a method step or a feature of a method step.Analogously, aspects described in the context of a method step alsorepresent a description of a corresponding block or item or feature of acorresponding apparatus.

Various elements and features of the present invention may beimplemented in hardware using analog and/or digital circuits, insoftware, through the execution of instructions by one or more generalpurpose or special-purpose processors, or as a combination of hardwareand software. For example, embodiments of the present invention may beimplemented in the environment of a computer system or anotherprocessing system. FIG. 8 illustrates an example of a computer system350. The units or modules as well as the steps of the methods performedby these units may execute on one or more computer systems 350. Thecomputer system 350 includes one or more processors 352, like a specialpurpose or a general purpose digital signal processor. The processor 352is connected to a communication infrastructure 354, like a bus or anetwork. The computer system 350 includes a main memory 356, e.g., arandom access memory (RAM), and a secondary memory 358, e.g., a harddisk drive and/or a removable storage drive. The secondary memory 358may allow computer programs or other instructions to be loaded into thecomputer system 350. The computer system 350 may further include acommunications interface 360 to allow software and data to betransferred between computer system 350 and external devices. Thecommunication may be in the from electronic, electromagnetic, optical,or other signals capable of being handled by a communications interface.The communication may use a wire or a cable, fiber optics, a phone line,a cellular phone link, an RF link and other communications channels 362.

The terms “computer program medium” and “computer readable medium” areused to generally refer to tangible storage media such as removablestorage units or a hard disk installed in a hard disk drive. Thesecomputer program products are means for providing software to thecomputer system 350. The computer programs, also referred to as computercontrol logic, are stored in main memory 356 and/or secondary memory358. Computer programs may also be received via the communicationsinterface 360. The computer program, when executed, enables the computersystem 350 to implement the present invention. In particular, thecomputer program, when executed, enables processor 352 to implement theprocesses of the present invention, such as any of the methods describedherein. Accordingly, such a computer program may represent a controllerof the computer system 350. Where the disclosure is implemented usingsoftware, the software may be stored in a computer program product andloaded into computer system 350 using a removable storage drive, aninterface, like communications interface 360.

The implementation in hardware or in software may be performed using adigital storage medium, for example cloud storage, a floppy disk, a DVD,a Blue-Ray, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory,having electronically readable control signals stored thereon, whichcooperate (or are capable of cooperating) with a programmable computersystem such that the respective method is performed. Therefore, thedigital storage medium may be computer readable.

Some embodiments according to the invention comprise a data carrierhaving electronically readable control signals, which are capable ofcooperating with a programmable computer system, such that one of themethods described herein is performed.

Generally, embodiments of the present invention may be implemented as acomputer program product with a program code, the program code beingoperative for performing one of the methods when the computer programproduct runs on a computer. The program code may for example be storedon a machine readable carrier.

Other embodiments comprise the computer program for performing one ofthe methods described herein, stored on a machine readable carrier. Inother words, an embodiment of the inventive method is, therefore, acomputer program having a program code for performing one of the methodsdescribed herein, when the computer program runs on a computer.

A further embodiment of the inventive methods is, therefore, a datacarrier (or a digital storage medium, or a computer-readable medium)comprising, recorded thereon, the computer program for performing one ofthe methods described herein. A further embodiment of the inventivemethod is, therefore, a data stream or a sequence of signalsrepresenting the computer program for performing one of the methodsdescribed herein. The data stream or the sequence of signals may forexample be configured to be transferred via a data communicationconnection, for example via the Internet. A further embodiment comprisesa processing means, for example a computer, or a programmable logicdevice, configured to or adapted to perform one of the methods describedherein. A further embodiment comprises a computer having installedthereon the computer program for performing one of the methods describedherein.

In some embodiments, a programmable logic device (for example a fieldprogrammable gate array) may be used to perform some or all of thefunctionalities of the methods described herein. In some embodiments, afield programmable gate array may cooperate with a microprocessor inorder to perform one of the methods described herein. Generally, themethods are performed by any hardware apparatus.

While this invention has been described in terms of several advantageousembodiments, there are alterations, permutations, and equivalents whichfall within the scope of this invention. It should also be noted thatthere are many alternative ways of implementing the methods andcompositions of the present invention. It is therefore intended that thefollowing appended claims be interpreted as including all suchalterations, permutations, and equivalents as fall within the truespirit and scope of the present invention.

1. A user equipment, UE, for a wireless communication network comprisingone or more base stations, wherein the UE is configured to perform atransmission to a base station using a grant-free, GF, transmissionscheme, the transmission being performed in accordance with a GFtransmission configuration, wherein the UE is configured to receive fromthe base station a certain signaling, the certain signaling indicatingthat the base station failed to identify the UE from the transmission,and wherein, responsive to the certain signaling from the base station,the UE is configured to retransmit the transmission in accordance with aGF retransmission configuration, the GF retransmission configurationbeing different from the GF transmission configuration.
 2. The userequipment of claim 1, wherein the GF transmission configurationcomprises a GF transmission resource or a GF transmission resource pool,and the GF retransmission configuration comprises a GF retransmissionresource or a GF retransmission resource pool.
 3. The user equipment ofclaim 2, wherein the GF retransmission resource pool is larger than theGF transmission resource pool.
 4. The user equipment of claim 2, whereinthe GF retransmission resource pool comprises the GF transmissionresource pool and additional resources, or the GF retransmissionresource pool comprises resources different from the GF transmissionresource pool.
 5. The user equipment of claim 2, wherein the UE isconfigured to select the GF retransmission resource randomly from the GFretransmission resource pool.
 6. The user equipment of claim 2, whereinthe GF retransmission resource pool comprises a plurality ofretransmission resource pools, the plurality of retransmission resourcepools being of the same size or of different sizes, and the plurality ofretransmission resource pools comprising a first GF retransmissionresource pool and second GF retransmission resource pool.
 7. The userequipment of claim 6, wherein the UE is configured to select the GFretransmission resource from first GF retransmission resource pool andfrom second GF retransmission resource pool randomly, or based on aUE-ID or group/service type, e.g. UEs of a certain type use the first GFretransmission resource pool, and other UEs use the second GFretransmission resource pool.
 8. The user equipment of claim 6, whereinthe GF retransmission resource pool comprises at least one further GFretransmission resource pool.
 9. The user equipment of claim 1, whereinthe GF transmission configuration comprises a GF transmission codingscheme, and the GF retransmission configuration comprises a GFretransmission coding scheme, the GF transmission coding scheme beingdifferent from the GF retransmission coding scheme.
 10. The userequipment of claim 9, wherein the GF transmission coding schemecomprises a first NOMA sequence, and the GF retransmission coding schemecomprises a second NOMA sequence, the second NOMA sequence being morerobust than the first NOMA sequence, e.g., by using a lower code rate.11. The user equipment of claim 1, wherein the GF transmissionconfiguration comprises a time at which the transmission is performed,and the GF retransmission configuration comprises a plurality of timeoffsets for the retransmission relative to the time of the transmission.12. The user equipment of claim 11, wherein the UE is configured toselect, based on a UE-ID or a group/service type, from the plurality oftime offsets randomly a time offset for the retransmission, or apreconfigured time offset for the retransmission.
 13. The user equipmentof claim 12, wherein UEs of a certain type use a preconfigured timeoffset, and other UEs use a random time offset.
 14. The user equipmentof claim 1, wherein the GF transmission configuration comprises oridentifies a plurality of grant-free access occasions during whichgrant-free transmissions are to be performed, the plurality ofgrant-free access occasions comprising at least a first grant-freeaccess occasion and a second grant-free access occasion, and the GFretransmission configuration comprises or identifies at least onefurther grant-free access occasion during which grant-freeretransmissions are to be performed, the further grant-free accessoccasion being different from the second grant-free access occasion. 15.The user equipment of claim 14, wherein first UEs, e.g., latencysensitive UEs or services, like URLLC services, use a further grant-freeaccess occasion that is earlier than the second grant-free accessoccasion, and second UEs, e.g., less sensitive UEs or services, likeenhanced Mobile BroadBand, eMBB, massive Machine-Type Communication,mMTC, or IoTs, use a further grant-free access occasion that is later orearlier than the second grant-free access occasion.
 16. The userequipment of claim 1, wherein the UE is preconfigured with a pluralityof GF retransmission configurations, e.g., using an UE specific RRCsignaling, and the UE is configured to receive a control message, like aDCI message, indicating which of the plurality of GF retransmissionconfigurations is to be used by the UE responsive to the certainsignaling, or the UE is configured to receive a control message, like aDCI message, indicating a plurality of GF retransmission configurations,and wherein the certain signaling indicates which of the plurality GFretransmission configurations is to be used by UE responsive toreceiving the certain signaling, or the certain signaling comprises theGF retransmission configuration to be used by UE responsive to receivingthe certain signaling
 17. A wireless communication system, comprising:one or more UEs of claim 1, and one or more base stations, BSs, whereinthe BS is configured to serve one or more UEs of the wirelesscommunication network, wherein a certain number of the UEs, which areserved by the BS, are configured to perform a transmission to the BSstation using a grant-free, GF, transmission scheme, the transmissionbeing performed in accordance with a GF transmission configuration, theBS is configured receive from the certain UEs respective grant freetransmissions and to determine whether the certain UEs can be identifiedfrom the grant free transmission, and in case some or all of the certainUEs cannot be identified by the BS, the BS is configured to transmit acertain signaling, the certain signaling indicating that the BS failedto identify the certain UEs from the transmission, and causing thecertain UEs to retransmit the transmission in accordance with a GFretransmission configuration, the GF retransmission configuration beingdifferent from the GF transmission configuration.
 18. A method,comprising performing by a user equipment, UE, of a wirelesscommunication network, which comprises one or more base stations, atransmission to a base station using a grant-free, GF, transmissionscheme, the transmission being performed in accordance with a GFtransmission configuration, receiving, at the UE, from the base stationa certain signaling, the certain signaling indicating that the basestation failed to identify the UE from the transmission, and responsiveto the certain signaling from the base station, retransmitting, by theUE, the transmission in accordance with a GF retransmissionconfiguration, the GF retransmission configuration being different fromthe GF transmission configuration.
 19. The method of claim 18,comprising serving, by a base station, BS, of a wireless communicationnetwork, which comprises one or more base stations, one or more UEs ofthe wireless communication network, wherein a certain number of the UEs,which are served by the BS, perform a transmission to the BS stationusing a grant-free, GF, transmission scheme, the transmission beingperformed in accordance with a GF transmission configuration, receiving,by the BS, from the certain UEs respective grant free transmissions anddetermining whether the certain UEs can be identified from the grantfree transmission, and in case some or all of the certain UEs cannot beidentified by the BS, transmitting, by the BS, a certain signaling, thecertain signaling indicating that the BS failed to identify the certainUEs from the transmission, and causing the certain UEs to retransmit thetransmission in accordance with a GF retransmission configuration, theGF retransmission configuration being different from the GF transmissionconfiguration.
 20. A non-transitory digital storage medium having acomputer program stored thereon to perform the method comprisingperforming by a user equipment, UE, of a wireless communication network,which comprises one or more base stations, a transmission to a basestation using a grant-free, GF, transmission scheme, the transmissionbeing performed in accordance with a GF transmission configuration,receiving, at the UE, from the base station a certain signaling, thecertain signaling indicating that the base station failed to identifythe UE from the transmission, and responsive to the certain signalingfrom the base station, retransmitting, by the UE, the transmission inaccordance with a GF retransmission configuration, the GF retransmissionconfiguration being different from the GF transmission configuration,when said computer program is run by a computer.